This invention relates to X-ray imaging systems. More specifically this application relates to X-ray imaging systems utilizing a pixelated X-ray source and a X-ray detector operated synchronously. The imaging system may be used in industrial and medical applications.
X-ray imaging systems have many applications in industrial and medical fields. In the medical field X-ray imaging is often used for cancer screening. Early detection of cancer leads to earlier treatment and higher cure/success rates. A technology which provides for earlier detection of cancers, in a more dose-efficient manner, will have significant impact on cancer treatment.
Currently, nearly all medical screening and diagnosis is based on 2-D X-ray xe2x80x9cprojection imagingxe2x80x9d. A xe2x80x9cfloodxe2x80x9d of X-ray illumination is used to either expose film, or more recently, a (coarse) array of X-ray sensitive imaging electronics. The spatial and coherence attributes of the X-ray source have not been fundamentally altered since the original inception. The underlying tissue structure determines what X-ray fluence, or uniform X-ray exposure is required for adequate imaging. This 2-D projection imaging suffers from scatter and from the superposition of many images through the tissue thickness.
One approach to mitigating scatter has been by employing an xe2x80x9cinvertedxe2x80x9d detector topology in which a single, small area detector is xe2x80x9calignedxe2x80x9d with a scanning beam. This approach did not benefit from X-ray focusing and, as a result resulted in poor system efficiency. Nevertheless, the system did uncover some of the benefits in eliminating scatter by producing cardiac images with good image quality, S/N and reduced dosage. Another system is based on xe2x80x9cslot-scanningxe2x80x9d. This relies on a mechanical translation of a narrow X-ray sensor and the rotation of a X-ray source. While scatter rejection is improved above the current systems, it still uses flood X-ray illumination within the irradiated slot and a cumbersome CT implementation. Also because of the lack of good X-ray focusing, it has poor energy utilization from the X-ray head.
The potential resolution capabilities of X-ray imaging are hardly being exploited. The currently approved digital systems have less high-resolution information than the current film systems. Thus cancers associated with micro-calcifications are more likely to either go under or undetected, or get passed onto biopsy analysis. Both results are undesirable. Except for the two xe2x80x9cscannedxe2x80x9d systems mentioned above, the current systems rely on unsophisticated scatter-rejection techniques based on xe2x80x9cpassivexe2x80x9d concepts such as geometric enlargement, or mechanical grids. While these passive scatter rejection grids do improve image quality (S/N), they do so at the expense of greatly increasing the dosage to the patient.
The present invention is directed to a high-resolution, volumetric imaging system based on active-scanning and detection of X-rays. X-rays are uniquely suited to high-resolution imaging of deep structures. However, current X-ray imaging technology, including the recently approved flat-panel detectors, are all based on a nearly xe2x80x9cuniformxe2x80x9d illumination of X-rays. The newer, systems based on xe2x80x9cslotxe2x80x9d scanning, though reducing scatter, still rely on uniform, X-ray exposure. Consequently, none of these systems are xe2x80x9cadaptivexe2x80x9d within the field of view.
The present invention is directed to a system architecture and component technology that fundamentally changes the current approach and will allow for adaptive exposure within a given field of view. Stereographic, and tomographic systems can be based on this technology will eliminate image degradation due to scatter. This will provide for optimum X-ray exposure conditions, improved diagnostic images, improved patient comfort and utilization and reduced patient dosage. The complete system can be implemented without moving parts and can be entirely electrically addressed. As a result, it will be less expensive than other tomographic or CT approaches. This technology will result in a higher performance, more sensitive system.
The present invention provides the following key contributions:
Active scanning through an electrically addressable array of X-ray emitters producing a narrow beam of X-rays.
High resolution, active-pixel detection based on CCD/CMOS electronics/detectors and microchannel based high-resolution scintillation technology.
Synchronized and adaptive emission and detection resulting in scatter rejection, improved image quality, and optimum exposure and dose reduction. The X-ray emitting and sensing devices are completely electronically addressable and scaleable. Alternatively, a mechanically moving aperture can be utilized in front of the X-ray detector.
The present invention provides: several times the amount of diagnostic information while reducing exposure levels, a reduction in scatter while reducing X-ray exposure, with high image resolution. The present invention can uncover low-density, low-contrast images that is currently obscured by overlapping tissue structure and can provide pixel-by-pixel automatic-exposure.
Our previous work in the design and construction of microchannel based X-ray screens for use in X-ray systems can be found in U.S. Pat. No. 5,952,665; issued Sep. 14, 1999 Entitled Composite Nanophosphor Screen for Detecting Radiationxe2x80x9d; U.S. Pat. No. 6,300,640 issued Oct. 9, 2001 Entitled xe2x80x9cComposite Nanophosphor Screen For Detecting Radiation Having Optically Reflective Coatingsxe2x80x9d, PCT published application No. WO 99/28764; U.S. patent application Ser. No. 09/688,662 filed Oct. 16, 2000 Entitled xe2x80x9cHigh Resolution High Output Microchannel Based Radiation Sensorxe2x80x9d; U.S. patent application Ser. No. 09/385,995 filed Aug. 30, 1999 Entitled xe2x80x9cMicrochannel High Resolution X-ray Sensor Having an Integrated Photomultiplierxe2x80x9d, and U.S. patent application Ser. No. 10/073,702 filed Feb. 11, 2002 Entitled xe2x80x9cHigh Resolution Tiled Microchannel Storage Phosphor Based Radiation Sensorxe2x80x9d. The disclosures of these previous US patent applications and issued patents are hereby incorporated by reference as if fully set forth herein.